The invention relates to a compound needle with a slider used for opening and closing the yarn chamber.
A compound needle with a two-section slider is known from DE 25 37 502. The compound needle has an elongated base body, which makes a transition into a hook at one end. A slider slit, in which the slider is arranged, starts at a location opposite the open side of the hook. The slider has two slider springs which rest flat against each other and together can be pushed toward the hook and away from it in the slit. The ends of the two slider springs are bent away from each other at their edges facing the hook in order to form a funnel for receiving the hook tip.
In the course of operating the needle it is necessary to assure that the hook tip always dependably finds its way into the funnel during opening and closing of the yarn chamber. If the slider springs contact the hook tip because of external influences or because of advanced wear, malfunctions will occur.
A compound needle is known from DE 199 13 822 C2, whose slider is also composed of two slider springs. Together they form a funnel at their free ends, but are otherwise convexly bent away from each other. The lateral bulge of the slider springs is used for centering it in the slider slit, so that the funnel formed by the slider springs can be pushed well centered over the hook tip.
A particularly great functional dependability in respect to centering the hook in the funnel is obtained when the funnel is embodied to be as large as possible. However, an enlargement of the funnel entails difficulties, because the funnel enters the slider slit when the slider is retracted. Here, funnels of increased size tend to increase the friction, which in turn can result in wear and/or heat generation. This in turn negatively affects the ability of the compound needle as a whole to function, wherein in the extreme case the slider springs can no longer be moved with the required ease.
Based on this it is the object of the invention to create a compound needle which, along with reduced slider friction, permits a high degree of operational dependency.
This object is attained by means of a compound needle having the characteristics of claim 1.
The compound needle of the invention has a slider with two slider springs. The slider can be made of one piece or of several individual elements (slider spring, slider body), which are releasably or permanently connected with each other. The ends of the slider springs are embodied to be tapered. Thus, the thickness of the slider springs continuously decreases towards the ends of the slider springs in a tapered area, which is limited to the funnel area. With a given exterior funnel width, this results in a larger interior funnel width, so that the dependability with which the slider is pushed over the hook increases even under difficult conditions and with advanced wear. Since the exterior contour of the funnel no increase of friction occurs. On the contrary, it is possible in the reverse manner to reduce the exterior width of the funnel, so that a funnel is obtained with the same funnel width as was found in connection with customary compound needles.
It is also possible to make use of both the effects described here separately, namely an increase of the inner width of the funnel, combined with a reduction of its exterior width. In comparison with customary compound needles, such a compound needle shows decreased friction and improved functional dependability.
It can be practical to provide only one of the slider springs with a taper and to embody the other one in the customary manner with a non-tapered end. This is particularly sensible in those cases in which the slider is subjected to a known lateral loop tension or other laterally acting force. However, in general a symmetrical (mirror symmetrical) embodiment of the slider springs is preferred, so that the dependable aim of the slider and the hook is generally increased.
The tapering of the slider springs is expressed in a reduction of the thickness of the slider springs measured transversely in respect to the movement direction and at right angles in respect to the lateral faces of the compound needle. In this case the reduction in thickness is continuous. The free ends of the slider springs are preferably rounded with a very small radius of curvature. Preferably no sharp edges are provided at the free end of the slider spring. This prevents damage or injury to the knitted fabric and/or to the yarn.
The tapered area is preferably shorter than the funnel. In other words, the tapering of the slider springs is limited to their area in which they are spread apart from each other.
It is also possible to limit the taper to an even shorter section, for example merely to a portion of the funnel. This increases the stability of the slider springs in their funnel area.
The slider springs can have an approximately rectangular cross section in their tapered area. This is achieved by a simple flattening of the slider springs which are bent away from each other. Alternatively it is possible to limit the taper to a central portion of the slider spring, for example, so that it is then provided with a depression for receiving the hook on its inside, which deepens and widens in the direction toward the free ends of the slider springs. This measure, too, can improve the properties of the needle, as recited above, wherein an increased stability of the slider springs is achieved in addition.
Further details of advantageous embodiments of the invention ensue from the description, the drawings, or the dependent claims.